This invention relates to a printer and a facsimile apparatus using the printer and, more particularly to a printer which prints an image on a print medium in accordance with an ink-jet printing method and a facsimile apparatus using the printer.
Conventionally, a printer which uses a printhead, comprising a plurality of nozzles, to print an image on a print medium by discharging ink droplets from the nozzles, is known as an ink-jet printer. Recently, a facsimile apparatus employing this ink-jet printer as a printing unit has been proposed.
As a printhead of the printing unit, as well as a monochrome printhead which uses only black ink for monochrome image printing, a color printhead which supplies yellow, magenta, cyan and black color ink to nozzles and discharges ink from the nozzles each assigned to each of the four color ink, thus performs color printing is provided.
However, in the above-mentioned ink-jet printer, if the amount of residual ink is small upon image printing, a printed image may have an unprinted area due to failure of ink discharge on a print medium or an image area of degraded image quality due to abnormality in printing, thus normal image printing cannot be performed. In this case, the printed image lacks image quality worthy of a document. Since such printing has no value, print medium is wasted.
In development and improvement of ink-jet printer, various residual-ink detection methods have been considered, taking the above drawback into consideration. Known examples are, (1) detecting existence/absence of ink within an ink container (ink tank) by 1 detecting electric conductivity between a pair of electrodes provided in the container; 2 detecting transmittance of irradiated light or quantity of reflection light; (2) detecting change of weight of the ink tank; (3) printing a test pattern on a print medium, and detecting the condition of the printed test-pattern image, to judge whether or not ink discharge has been normally performed; and (4) detecting discharge/undischarge of ink.
When image printing cannot be normally performed as described above, ink-discharge failure may be caused by, not only decreased residual ink or ink exhaustion, but discharge orifices clogged with ink having increased viscosity as it dries. As the latter case may occur even when the amount of residual ink is large, the above methods of detecting ink within an ink container by using electrodes or an optical sensor can hardly detect this phenomenon. On the other hand, the method of detecting the condition of printed image or detecting discharged ink droplets can detect the ink-discharge failure.
In a facsimile apparatus, facsimile image printing is instructed via a telephone line, and image data to be print-outputted is also transmitted via the telephone line. Generally, the facsimile apparatus does not store all the received image data, but when printing for some area has been completed, deletes image data corresponding to the printed area from a memory. This reduces the requirement for memory capacity and reduces costs of the apparatus.
As described above, in the facsimile apparatus using the ink-jet printer as its printer unit, image printing may not be normally performed regardless of residual ink amount. In such case, if it is judged that ink remains, an image of degraded image quality is printed. On the other hand, as received data used in printing is deleted from a memory, to re-print based on the deleted data, it is necessary to request a transmitting side to re-transmit the data, which increases a user's labor. Accordingly, in the facsimile apparatus, it is desirable to employ the method of detecting the condition of printed image and/or the method of detecting ink-discharge status, which enables to detect not only decreased residual ink amount but degradation of ink discharge due to clogged nozzles.
However, there is a possibility that ink-discharge failure occurs after it is judged that ink discharge is normally performed. Accordingly, it is undesirable to delete image data immediately after image printing, since if ink-discharge failure occurs at that point, the image data is deleted from the memory although an image has not been normally printed.
Further, as the facsimile apparatus employing the above-mentioned ink-jet printer as a printing unit, a facsimile apparatus having a function to be connected to a host device such as a computer, similar to general printers, and prints image based on data from the host device has been proposed. Generally, in operation as a facsimile apparatus, image formation is performed by using only black ink, while in case of image printing based on data from a connected host device, color image printing is possible by using the aforementioned color printhead.
In the method of judging the condition of printed image and the method of discharging ink and judging the discharge status, ink is used upon detection. When the color printhead is attached to the facsimile apparatus but the apparatus performs facsimile reception printing, if ink-discharge status is judged with respect to other color ink than black ink, the other color ink are wasted.